Technical Field
[0001] The invention refers to transport networks carrying circuit data flows, of the synchronous
and asynchronous type, employing either space, time, frequency or wavelength multiplexing,
and specifically refers to a procedure for sorting circuit data flows in a sub-network.
Background Art
[0002] As known, data are transmitted in TDM (Time Division Multiplexing) transport networks
in time windows or sets of slots (called "time slots") whose length is fixed, each
of which contains one or more circuit data flows defined by the implemented protocol.
Networks of this kind include, for example, SDH (Synchronous Digital Hierarchy) or
SONET (Synchronous Optical Network) networks. The term "slot" therefore means "time
interval" in this case.
[0003] In WDM (Wavelength Division Multiplexing) networks, data are transmitted on different
wavelengths λ
i, which replace the multiplexing time slots and consequently may be called "λ-slots".
Similarly, SDM (Space Division Multiplexing) or FDM (Frequency Division Multiplexing)
networks can be implemented, in which case the concept of slot is associated to intervals
of space or frequency. Specifically, FDM technology was implemented in the past before
TDM technology was developed.
[0004] The invention refers to all types of networks based on the concept of slot described
above. Reference will be made in the description that follows to TDM (SDH and SONET)
and WDM networks considering their current popularity.
[0005] From a technical point of view, time slots in SDH and SONET networks and λ-slots
in WDM networks can be considered equivalent. They are both "containers" in which
data are transmitted, regardless of the actual physical implementation of the network.
[0006] Each transport network, SDH, SONET or WDM, can comprise various sub-networks, e.g.
ring networks or meshed sub-networks, all employing the same transmission protocol.
[0007] When a circuit data flow set to be sold to a customer is created and established
for operation, the slots forming the sub-network (time slots for SDH or SONET, λ-slots
for WDM) are allocated to each circuit according to the situation of the network at
the time; the situation is randomly determined by the incoming requests (according
to the typical criteria of the network operator). In general, the aim is to optimise
the total occupied band to minimise network implementation investments. Calculation
algorithms have been developed for this purpose to optimise sub-network load and reduce
band occupation. The traffic demand to be carried by the network must be entirely
defined beforehand to work these theoretical algorithms, which in practice is impossible.
[0009] The algorithm described in this publication is very useful for calculating optimal
distribution of flows given a known demand, e.g. for programming a new ring sub-network.
The biggest problem, on the other hand, to be faced when optimising a sub-network
which is already operational in terms of occupied band, is how to change circuit configuration
to implement the optimised configuration without disrupting the service, with minimum
effects perceived by customers.
[0010] Flows are often untidy and irregular in a sub-network that has been working for some
time due to flow allocation changes which inevitably occur in the course of time.
For example, the allocated flows are released and "gaps" in the slot allocation map
are formed when the resources allocated to a customer are cleared following cancellation
of contracts. These gaps are often employed for smaller flows and even smaller gaps
are created, which are even more difficult to use in the future. This effect in the
middle term progressively worsens the ratio between the band effectively occupied
by data in the sub-network and the total available band of sub-network, making the
configuration of new flows in the sub-network effectively impossible.
[0011] Procedures for the temporary or definitive re-allocation of time slots in a TDM network
are also known, e.g. the procedure illustrated in document
WO 97/36402.
[0012] Despite referring to a switched network, this patent describes a procedure for shifting
one or more time slots from a primary node to a temporary node and then re-allocating
the time slots back to the primary node. This procedure is used to deal with the unexpected
request for resources on the primary node by one or more customers and is used to
temporarily allocate some time slots to an adjacent secondary node. The document shows
how it is possible to work on time slot allocation, by shifting and exchanging them,
without incurring excessive disruption for customers.
[0013] The object of this invention is to propose a procedure for dealing with the problem
of how to optimise the band occupied by a plurality of circuit data flows in a transport
sub-network while keeping the network running and causing the least possible disruption
to customers for each single flow.
[0014] This and other objectives are obtained by means of an optimisation procedure and
corresponding management device as illustrated in the annexed claims.
Summary of the invention
[0015] Advantageously, according to the invention, a flow sorting procedure is applied to
reduce the occupied band and release a plurality of time slots, which would otherwise
be occupied, for new customers.
[0016] In this way, when a sub-network is apparently saturated because there is no space
for allocating a new data flow, the procedure described herein may be applied to optimise
the band occupied by the current flows and possibly sort the sub-network to create
space for the new flows. The result is a procedure for optimising the band employed
by the flows configured on the sub-network which preserves the theoretical qualities
of an optimal routing algorithm combining the possibility of minimising the number
of operations required to reach this condition.
Brief Description of Drawings
[0017] Additional characteristics and advantages of the invention in its preferred form
of embodiment will now be described, by way of example only, with reference to the
annexed drawings wherein:
figure 1 is a logical diagram of a ring transport sub-network;
figure 2a is a table schematically illustrating an initial (non optimised) flow situation
in a ring sub-network;
figure 2b is a table schematically illustrating the theoretical distribution of flows
in the ring sub-network in figure 2a, after applying a theoretical routing algorithm;
figure 2c is a table schematically illustrating the final distribution of flows in
the ring sub-network in figure 2a, after applying a sorting procedure according to
the invention;
figures 3, 4 and 5 schematically illustrate how the sorting procedure according to
the invention is applied, for example on a simplified sub-network; and
figure 6 illustrates some steps in the sorting procedure referred to the simplified
sub-network example shown in figure 3.
Detailed description of the preferred embodiments
[0018] The following detailed description illustrates a flow sorting procedure in a transport
network ring sub-network carrying circuit data flows. The sub-network is schematically
shown as a set of slots (which are time, spatial, frequency or wavelength intervals
between pairs of linked sites). Specifically, the illustrated procedure can be applied
to sorting SDH/SONET (Time Division Multiplexing) type networks and WDM (Frequency
Division Multiplexing) type networks. The term "slot" will be used to indicate "time
slots" in the case of SDH/SONET networks and "λ-slots" in the case of WDM networks.
[0019] Similarly, the invention can be applied to networks in which data flow multiplexing
is obtained through either space division (SDM, Space Division Multiplexing) or frequency
division (FDM, Frequency Division Multiplexing), in which case the term "slot" will
be associated to space and frequency intervals, respectively.
[0020] The ring sub-network may implement MS-SPRing technology (OMS-SPRing for WDM networks).
The procedure may be applied in general to any sub-network which may also not be ring
structured (e.g. meshed or mixed meshedring topologies); flows may be protected or
not.
[0021] With reference to figure 1, an example of sub-network on which to apply the invention
is a ring essentially consisting of six nodes, geographically placed in six different
locations called X1, X2, X3, X4, X5, X6 in the figure, reciprocally connected by optical
fibres or other transmission medium 9.
[0022] The logical diagram of the ring shown in figure 1 consists of a slot matrix (like
that shown in figures 2a, 2b and 2c) where the rows indicate multiplexed slots (e.g.
from 1 to 16) according to the particular transmission protocol and the columns 6
indicate the slots with the same transmission index which can be exploited to configure
the circuits (sets of slots with the same numeric code) between the various locations
reached by the ring.
[0023] The flows are identified inside the table by a reference index, i.e. a number written
inside each of the boxes allocated to a certain flow. For example, boxes 7a and 7b
are allocated to flow 9 which occupies the set of slots 9 in the sections X6-X1 and
X1-X2, while boxes 8a and 8b are allocated to flow 15 which occupies the set of slots
16 in the sections X1-X2 and X2-X3.
[0024] It is immediately apparent that the flows in the ring network in figure 2a are distributed
untidily and partially occupy all sixteen sets of slots 6. The sixteen sets of slots
occupied by the flows form a total of 16•6=96 available slots, of which up to 44 remain
"free" between flows (blank boxes in the table). This means that despite being all
engaged, only 54% of the slots 6 in the ring are actually occupied; sub-network use
is therefore not very efficient and collocating new flows in the ring may be difficult,
if not impossible.
[0025] The band occupied by the currently allocated flows can be reduced and a certain number
of slot sets may be entirely released, as illustrated in detail below, by applying
a flow sorting procedure to the slot sets in the initial conditions of the sub-network
as shown in figure 2a.
[0026] The flow sorting procedure is essentially based on the following sequence of operations:
- Calculating theoretical optimal flow routing with the objective of minimising "gaps"
(band optimisation process) to obtain the configuration illustrated, for example,
in figure 2b, starting from instantaneous filling data of a ring sub-network. A theoretical
optimisation algorithm for optimising traffic in known demand conditions is used to
obtain this result, e.g. the algorithm described in the aforesaid publication GON KIM, DONG-WAN TCHA, Optimal Load Balancing on Sonet Bidirectional Rings, Dankook
University, July 1996;
- Comparing the original data and the theoretical condition calculated in the previous
step to define an optimal transition sequence and obtain an optimal final condition
with the constraint of minimising the number of flow position variations.
[0027] The procedure hereof determines a shifting sequence which minimises the use of slot
sets external to the ring and reduces, when possible, the number of shifts of each
flow.
[0028] For example, it would not be problem if the destination slot set of a single flow,
called A for example were free; on the other hand, if the destination slot were also
only partially engaged by another flow, called B, B would have to be shifted before
A and so on. An order can be formed by scanning the flows in the ring. The shifting
process may proceed seamlessly, one flow at a time, by respecting the order.
[0029] A slot will only need to be temporarily shifted onto a spare slot set (internal or
external to the ring), when the order becomes a loop, e.g. A>B>C>A; all the other
flows will be shifted and finally the flow shifted onto the spare slot will be moved
back to its destination.
[0030] A spare slot set can be a set of free slots in the same sub-network or a set of slots
located in different systems which share the same infrastructure, cable or installation
site. During this phase, one or more flows may need to be temporarily re-routed off
the sub-network and shifted back inside the ring. However, it is more cost-effective
to sort the flows in the ring without shifting temporarily onto other rings or alternatively
to minimise such shifts.
[0031] We will now analyse the sorting procedure step-by-step.
[0032] The first step in the procedure consists in calculating an optimal theoretical flow
configuration for the occupied band by means of the theoretical optimal flow routing
algorithm. This configuration is illustrated in figure 2b, which clearly shows that
all the previously allocated flows in the ring have been "compacted" into the first
nine slot sets of the sub-network and the last seven are entirely free. The routing
criterion was changed for some flows, e.g. flow 1 and flow 10, from minimum to complementary
or vice versa, to occupy some slots which could not otherwise be employed.
[0033] The nine sets of slots occupied by the flows contain a total of 9•6=54 slots, of
which only 8 are "free" between flows (blank boxes in the table). This means that
up to 85% of the slots are actually occupied.
[0034] The second step consists in exchanging the slot sets in the theoretical flow configuration
shown in figure 2b and calculated in the previous step to obtain a new arrangement
of the slot set in which the number of flows is maximised and whose position corresponds
of the position assumed by the flows in the initial configuration in figure 2a. The
result of these exchanges is illustrated in the table in figure 2c and is also the
final objective of the sorting procedure.
[0035] The configuration shown in figure 2c is equivalent, as far as the occupied band is
concerned, to the configuration in figure 2b. The flows are distributed over 9 slot
sets containing a total of 9•6=54 slots. Also in this case, only 8 slots remain "free"
between flows (blank boxes in the table) and 85% of the slots is actually occupied
by the flows.
[0036] To better understand the steps of the sorting procedure, we will now consider a very
simplified sub-network (e.g. illustrated in figure 3) . The table in figure 3 contains
five rows, corresponding for example to the five sections of a ring, and six columns
corresponding to six sets of slots. This example is provided only to illustrate how
the slot sets are exchanged and the flows are shifted.
[0037] We will now assume that the configuration illustrated in figure 4 is obtained by
applying a theoretical optimal flow routing algorithm, corresponding to the first
step in the procedure.
[0038] The configuration shown in figure 5, where all the slot sets in the table in figure
4 have been exchanged according to a set of rules which will be described below, is
obtained by applying the second step.
[0039] Specifically, the second step consists of the following phases:
- a) Creating a first table in which each row shows for each flow whose position differs
from the initial theoretical flow configuration, a reference index associated to said
flow and a pair of values indicating the source slot set and the destination slot
set, respectively.
For example, for flow F, the string "F (5,1)", which means that flow F has slot set
5 as source (figure 3), and slot set 1 as destination (figure 4), will be written
in a first row of the table. The string "D (1,2)" will be used for flow D, and so
on for all the other flows whose position changes.
- b) Creating a list showing all pairs of values present at least once in said first
table, sorting (in decreasing order) said pairs of values according to the number
of times that each pair appears in said first table.
The most frequent shifts will be visible in the way.
- c) Exchanging the slot sets corresponding to the values indicated by the first pair
in said list from the top and deleting the first pair and all the other pairs from
the list in which either one or the other of the values contained in the first pair
occur.
- d) Repeating step c) until all the pairs in the list are finished.
The slot steps are exchanged during these last two phases starting from those corresponding
to the most frequent shifts.
The third step in the procedure consists in defining and performing a minimum shift
sequence concerning the single flows needed to shift each single flow from an initial
position occupied in the initial flow configuration (figure 3) to a final position
(figure 5) corresponding to the position shown by the flow in the optical slot set
arrangement. The operations performed in this third step, referred to the simplified
case illustrated in figures from 4 to 6, are summarised in figure 6 to which reference
is made below.
The following operations are required to implement the third step:
- e) Creating a second table showing flow interdependence.
See table 10a in figure 6.
- f) Selecting a first flow from those that must be shifted.
We will take flow A as an example.
- g) Adding a number of rows equal to the number of flows which occupy the final position
of said flow (also partially) in table 10a for the selected flow A and writing a pair
of reference indexes in each row indicating the selected flow and the flow occupying
the final position, respectively, or, if said final position is free, a pair of reference
indexes in which the first index indicates the selected flow and the second index
conventionally shows that the final position is free.
In the example shown, considering initially flow A, for example, the pair (A, C) has
been written in the table because flow A must be moved before flow C.
- h) Repeating step g) recursively selecting one by one the flows which occupy the final
position of the previously selected flow until such final position is either free
or occupied by a previously selected flow.
The pair (C, B) is therefore written in table 10a indicating that flow C requires
the precedence of flow B and finally (B, A) because flow B requires the precedence
of flow A.
- i) Checking in the second table the presence of circular dependence between two or
more flows; if such occurrence is present, starting to shift one of the flows in the
circular dependency onto a free spare slot set and for all pairs in the second table
having as the value indicative of the final position of the flow the index of the
shifted flows, replacing the index with a value conventionally indicating that the
final position is free, e.g. 0 (zero).
A circular dependency is present (A, C) - (C, B) - (B, A) in table 10a. Consequently,
the flow A is shifted onto a spare slot set (this operation is indicated by reference
20a in figure 6) and table 10a is updated. The result is table 10b in which flow A
is replaced by 0 conventionally indicating that the final position of flow B is now
free.
- j) Searching the second table for pairs whose index corresponds to the conventional
value (zero) showing that the final position is free and proceeding for each of the
pairs shifting the corresponding flow onto the corresponding final position and deleting
the row corresponding to said pair from the table; for all pairs in the second table
whose final position flow identification value corresponds to the identification index
of said shifted flow, replacing said index with a value 0 conventionally indicating
that the final position is free.
The operation indicated by reference 20b in figure 6 is therefore carried out, shifting
flow B from time slot 3 to time slot 1 and updating the table by deleting the row
(B, 0) and changing pair (C, B) to (C, 0), see table 10c.
- k) Repeating steps i) and j) until said second table is empty.
[0040] This operation entails shifting flow C from time slot 5 to time slot 3, see operation
20c in figure 6, updating the table by deleting row (C, 0) and changing pair (A, C)
to (A, 0), see table 10d, and finally shifting flow A from the spare time slot to
the final position, i.e. time slot 5, operation 20d.
[0041] At this point, the order table 10e will be empty and the next operation can be started.
- 1) Selecting a new flow from those which must be shifted and repeating step g) and
the following steps.
[0042] At this point of the procedure, in the simplified example, the flows have all been
shifted and the final configuration shown in figure 5 has been reached.
[0043] It is important to note that the sorting procedure previously described with reference
to a ring sub-network must follow a preliminary evaluation of data provided in documentation.
The evaluation must be repeated employing the punctual data provided by the network
manager responsible for physical cross-connections for implementation.
[0044] Defining whether it is possible to physically sort the flows and consequently plan
the sequence of transitions for minimising the number will only be possible following
this new evaluation.
[0045] In operative terms, the sorting procedure is implemented by a device for centralisation
management of the transport network which supports and closely interacts with the
network manager as explained below with special reference to a ring sub-network implementing
MS-SPRing technology.
[0046] In the case of a ring sub-network implementing MS-SPRing technology, the previously
described procedure can be implemented, for example, by overlapping an SNCP protection
employing some of the previously released time slots.
[0047] This procedure involves routing SNCP protection branches onto free time slots in
the ring. Consequently, two or three time slots may need to be preventively released
before starting the procedure. Furthermore, before starting the procedure, there must
be no alarms on the ring causing MS-SPRing protection to switch.
[0048] The steps needed to implement the method are listed below:
- 1) Routing and activating flow SNCP protection branch as shown in the migration procedure
by network manager.
- 2) Overriding SNCP protection exchange by means of the management system.
- 3) Deactivating flow protection branch and removing routing.
[0049] The SNCP protection branch is routed onto the same multiplexed sections of the working
branch but on a different AU4 (Administrative Unit Level 4).
[0050] Additionally, these operations must be carried out on all flows in the ring involved
in the previous sorting algorithm (they can be run several times on the same flow).
[0051] The method requires 25-40 shifts in a fully loaded ring. MS-SPRing protection can
be up for the entire duration of the migration (flow reliability is not affected).
[0052] At least 2-3 time slots must be freed in the entire tool to carry out the exchange
sequence. Consequently, either the sorting procedure is carried out before the ring
is ended or some flows are temporarily shifted.
[0053] The resulting band saving is in the range of 20% of the installed structure. The
punctual results of the cases taken into consideration during experimental phases
show that peaks of 40% can be obtained according to the type of traffic on the ring
(traffic on directives, balanced, diagonal, unbalanced).
[0054] Punctual "design" of the sorting operation is needed to apply the procedure according
to the real configuration of the flows on the ring; this protects the quality/reliability
level of the flows concerned by the sorting operation.
[0055] The procedure according to the present invention can be implemented as a computer
program comprising computer program code means adapted to run on a computer. Such
computer program can be embodied on a computer readable medium.
1. Procedure for optimising the band occupied by a plurality of circuit data flows (7,
8, ..) located, according to an initial configuration, in a plurality of sets of slots
(6) of a transport network, by sorting said flows inside the same sets of slots, said
procedure being
characterised by the fact that it comprises the following steps:
- calculating, with a theoretical optimal flow routine algorithm, a theoretical configuration
of the flows contained in said initial configuration, which is optimised as regards
the occupied band;
- exchanging the sets of slots (6) of said theoretical flow configuration to obtain
an optimal arrangement of said sets of slots, in which the number of flows whose position
corresponds to the position assumed by the same flows in said initial configuration
is maximised;
- defining a minimum shift sequence of single flows needed to shift each single flow
from an initial position occupied in said initial flow configuration to a final position
corresponding to the position assumed by the same flow in said optimal slot set arrangement
(6);
- implementing said minimum shift sequence of single flows, thus obtaining a flow
configuration with a band occupation equivalent to said theoretical flow configuration.
2. Procedure as per claim 1, in which said exchange phase between the sets of slots (6)
is implemented with the following steps:
a) creating a first table in which each row gives, for each flow whose position in
the theoretical flow configuration differs from the initial configuration position,
a reference index associated to said flow and a pair of values indicating the source
slot set and the destination slot set respectively;
b) creating a list of all the pairs of values present at least once in said first
table, sorting in decreasing order said pairs of values according to the number of
times that each pair appears in said first table;
c) exchanging the slot sets (6) corresponding to the values indicated by the first
pair in said list from the top, and deleting from the list said first pair and all
the other pairs in which either one or the other of the values contained in the said
first pair appear;
d) repeating step c) until all the pairs in said list are finished.
3. Procedure as per claim 1 or 2, in which said transport network includes at least one
set of spare slots normally unoccupied by a flow, and in which said phases that define
a minimum shift sequence of the single flows, and that implement said sequence, are
implemented with the following steps:
e) creating a second table (10), showing flow interdependence;
f) selecting a first flow from those that must be shifted;
g) adding in said second table (10), for said selected flow, a number of rows equal
to the number of flows that occupy, even partially, the final position of said selected
flow, writing a pair of reference indexes showing the selected flow and the flow occupying
the final position in each of said rows, or in the event that said final position
is free, a pair of reference indexes in which a first index indicates the selected
flow and a second index conventionally shows that the final position is free (0);
h) repeating step g) selecting the flows that occupy the final position of the flow
selected previously, one at a time and recursively, until such final position is free
or is occupied by a flow that has already been previously selected;
i) checking in said second table the presence of a circular dependence between two
or more flows, if such occurrence is present, starting to shift one of the flows in
said circular dependency onto a free spare slot set and for all pairs in said second
table having as a value indicative of the final position of the flow the index indicative
of said shifted flow, replacing said index with a value (0) conventionally indicating
that the final position is free;
j) searching within said second table for pairs having as index indicative of the
final position of the flow said conventional value (0) indicating that the final position
is free, and proceeding, for each of said pairs by shifting the corresponding flow
onto the corresponding final position and deleting the row corresponding to said pair
from the same table; for all pairs of said second table having as the value indicative
of the final position of the flow the index indicative of said shifted flow, replacing
said index with a value (0) conventionally indicating the final position is free;
k) repeating steps i) and j) until said second table is empty;
l) selecting a new flow from those which must be shifted and repeating step g) and
the following steps.
4. Procedure as per one of the claims from 1 to 3, in which said sets of slots (6) in
which said flows are initially collocated are sets of slots of a first sub-network
of said transport network.
5. Procedure as per claim 4, in which said sets of spare slots are sets of slots of a
second sub-network of said transport network.
6. Procedure as per claim 5, in which said first sub-network and said second sub-network
are ring networks.
7. Procedure as per any one of the previous claims, in which said transport network is
a network of the SDH or SONET type and said slots are time-slots.
8. Procedure as per any one of the claims 1 to 6, in which said transport network is
a WDM type network and said slots are λ-slots, i.e. wavelengths.
9. Procedure as per any one of the claims from 1 to 6, in which said transport network
is an SDM type network and said slots are space intervals.
10. Procedure as per any one of the claims from 1 to 6, in which said transport network
is a FDM type network and said slots are frequency intervals.
11. Device for the centralised management of a transport network, in which data are arranged
in circuit data flows collocated in a plurality of sets of slots (6), including a
system for sorting said flows within said sets of slots, characterised by the fact that said system uses a procedure for optimising the band according to any
one of the previous claims.
12. A computer program comprising computer program code means adapted to perform all the
steps of any of claims 1 to 10 when said program is run on a computer.
13. A computer program as claimed in claim 12 embodied on a computer readable medium.
1. Verfahren zum Optimieren des durch eine Mehrzahl von Circuit-Datenströmen (7, 8, ...),
die gemäß einer Anfangskonfiguration in einer Mehrzahl von Sätzen von Zeitnischen
(6) eines Transportnetzes angeordnet sind, besetzen Bands durch Sortieren der Ströme
innerhalb derselben Sätzen von Zeitnischen, wobei das Verfahren durch die Tatsache
gekennzeichnet ist, daß es die folgenden Schritte aufweist:
- Berechnen einer theoretischen Konfiguration der in der Anfangskonfiguration, die
hinsichtlich des besetzen Bands optimiert ist, enthaltenen Ströme mit einem theoretischen
optimalen Strom-Programmalgorithmus;
- Austauschen der Sätze von Zeitnischen (6) der theoretischen Stromkonfiguration,
um eine optimale Anordnung des Sätze von Zeitnischen zu erhalten, in der die Anzahl
von Strömen, deren Position der durch dieselben Ströme angenommenen Position in der
Anfangskonfiguration entspricht, maximiert ist;
- Definieren eines minimalen Verschiebungsabfolge von einzelnen Strömen, die erforderlich
ist, um jeden einzelnen Strom von einer in der Anfangsstromkonfiguration besetzten
Anfangsposition zu einer Endposition entsprechend der durch denselben Strom in der
optimalen Zeitnischen-Satzanordnung (6) angenommenen Position zu verschieben;
- Realisieren der minimalen Verschiebungsabfolge von einzelnen Strömen, wodurch eine
Stromkonfiguration mit einer Bandbesetzung äquivalent der theoretischen Stromkonfiguration
erhalten wird.
2. Verfahren nach Anspruch 1, in dem die Austauschphase zwischen den Sätzen von Zeitnischen
(6) mit den folgenden Schritten realisiert wird:
a) Erzeugen einer ersten Tabelle, in der jede Reihe für jeden Strom, dessen Position
sich in der theoretischen Stromkonfiguration von der Anfangskonfigurationsposition
unterscheidet, einen zu dem Strom gehörigen Bezugindex und ein Paar von Werten, die
den Quellen-Zeitnischen-Satz bzw. den Ziel-Zeitnischen-Satz angeben, angibt;
b) Erzeugen einer Liste aller Paare von Werten, die zumindest in der ersten Tabelle
vorhanden sind, Sortieren der Paare von Werte gemäß der Anzahl von Malen, die die
Paare in der ersten Tabelle erscheint, in absteigender Reihenfolge;
c) Austauschen der Zeitnischen-Sätze (6) entsprechend den durch das erste Paar von
oben in der Liste angezeigten Werte, und Löschen des ersten Paars und aller anderen
Paare, in denen entweder einer oder der andere der in dem ersten Paar enthaltenen
Werte erscheint;
d) Wiederholen von Schritt c), bis alle Paare in der Liste beendet sind.
3. Verfahren nach Anspruch 1 oder 2, in dem das Transportnetz zumindest einen Satz von
übrigen Zeitnischen enthält, die normalerweise durch einen Strom unbesetzt sind, und
in dem die Phasen, die eine minimale Verschiebungsabfolge der einzelnen Ströme definieren,
und die die Abfolge realisieren, mit den folgenden Schritten realisiert werden:
e) Erzeugen einer zweiten Tabelle (10), die eine gegenseitige Stromabhängigkeit zeigt;
f) Auswählen eines ersten Stroms aus denen, die verschoben werden müssen:
g) für den ausgewählten Strom Hinzufügen einer Anzahl von Reihen gleich der Anzahl
von Strömen, die, auch teilweise, die Endposition des ausgewählten Stroms besetzen,
Schreiben eines Paars von Bezugsindizes, die den ausgewählten Strom und den die Endposition
besetzenden Strom zeigen, in jede der Reihen, oder, im Fall, daß die Endposition frei
ist, eines Paars von Bezugsindizes, in dem ein erster Index den ausgewählten Strom
anzeigt und ein zweiter Index herkömmlich zeigt, daß die Endposition frei ist (0);
h) Wiederholen von Schritt g), Auswählen der Ströme, die die Endposition des vorhergehend
ausgewählten Stroms besetzen, einen auf einmal und rekursiv, bis eine derartige Endposition
frei ist oder durch einen Strom besetzt ist, der bereits vorhergehend ausgewählt wurde;
i) in der zweiten Tabelle Überprüfen der Anwesenheit einer wiederkehrenden Abhängigkeit
zwischen zwei oder mehr Strömen, wenn eine derartige Erscheinung vorhanden ist, Beginnen
einen der Ströme in der wiederkehrenden Abhängigkeit auf einen freien übrigen Zeitnischen-Satz
zu verschieben und für alle Paare in der zweiten Tabelle mit dem Index, der den verschobenen
Strom anzeigt, als einem Wert, der die Endposition des Stroms anzeigt, Ersetzen des
Index durch einen Wert (0), der herkömmlich anzeigt, daß die Endposition frei ist;
j) innerhalb der zweiten Tabelle suchen nach Paaren mit dem herkömmlichen Wert (0),
der anzeigt, daß die Endposition frei ist, als einem Index, der die Endposition des
Stroms anzeigt, und für jedes der Paare Fortschreiten durch Verschieben des entsprechenden
Stroms auf die entsprechende Endposition und Löschen der Reihe entsprechend dem Paar
aus derselben Tabelle; für alle Paare der zweiten Tabelle mit dem Index, der den verschobenen
Strom anzeigt, als dem Wert, der die Endposition des Stroms anzeigt, Ersetzen des
Index durch einen Wert (0), der herkömmlich anzeigt, daß die Endposition frei ist;
k) Wiederholen der Schritte i) und j), bis die zweite Tabelle leer ist;
l) Auswählen eines neuen Stroms aus denen, die verschoben werden müssen, und Wiederholen
von Schritt g) und den folgenden Schritten.
4. Verfahren nach einem der Ansprüche 1 bis 3, bei dem die Sätzen von Zeitnischen (6),
in denen die Ströme anfänglich angeordnet sein, Sätze von Zeitnischen eines ersten
Teilnetzes des Transportnetzes sind.
5. Verfahren nach Anspruch 4, in dem die Sätze von übrigen Zeitnischen Sätze von Zeitnischen
eines zweiten Teilnetzes des Transportnetzes sind.
6. Verfahren nach Anspruch 5, in dem das erste Teilnetz und das zweite Teilnetz Ringnetze
sind.
7. Verfahren nach einem der vorhergehenden Ansprüche, in dem das Transportnetz ein Netz
vom SDH- oder SONET-Typ ist und die Zeitnischen Zeitfenster sind.
8. Verfahren nach einem der Ansprüche 1 bis 6, in dem das Transportnetz ein Netz vom
WDM-Typ ist und die Zeitnischen λ-Zeitnischen, d.h. Wellenlängen sind.
9. Verfahren nach einem der Ansprüche 1 bis 6, in dem das Transportnetz ein Netz vom
SDM-Typ ist und die Zeitnischen Raumintervalle sind.
10. Verfahren nach einem der Ansprüche 1 bis 6, in dem das Transportnetz ein Netz vom
FDM-Typ ist und die Zeitnischen Frequenzintervalle sind.
11. Einrichtung zur zentralisierten Verwaltung eines Transportnetzes, in dem Daten in
Circuit-Datenströmen angeordnet sind, die in einer Mehrzahl von Sätzen von Zeitnischen
(6) angeordnet sind, einschließlich eines Systems zum Sortieren der Ströme innerhalb
des Satzes von Zeitnischen, gekennzeichnet durch die Tatsache, daß das System ein Verfahren zur Optimierung des Band gemäß einem der
vorhergehenden Ansprüche verwendet.
12. Computerprogramm mit einer Computerprogrammcodeeinrichtung, die geeignet ist, alle
Schritte irgendeines der Ansprüche 1 bis 10 durchzuführen, wenn das Programm auf einem
Computer läuft.
13. Computerprogramm nach Anspruch 12, das in einem computerlesbaren Medium enthalten
ist.
1. Procédure pour optimiser la bande occupée par une pluralité de flux de données de
circuit (7, 8, ..) situés, selon une configuration initiale, dans une pluralité de
séries de tranches (6) d'un réseau de transport, en triant lesdits flux à l'intérieur
des mêmes séries de tranches, ladite procédure étant
caractérisée en ce qu'elle comprend les étapes suivantes consistant à :
- calculer, avec un algorithme de routine de flux optimal théorique, une configuration
théorique des flux contenus dans ladite configuration initiale, qui est optimisée
en ce qui concerne la bande occupée ;
- échanger les séries de tranches (6) de ladite configuration de flux théorique pour
obtenir un agencement optimal desdites séries de tranches, dans lesquelles le nombre
de flux dont la position correspond à la position adoptée par les mêmes flux dans
ladite configuration initiale est maximisé ;
- définir une séquence de décalage minimum de flux individuels nécessaire pour décaler
chaque flux individuel d'une position initiale occupée dans ladite configuration de
flux initiale à une position finale correspondant à la position adoptée par le même
flux dans ledit agencement de séries de tranches optimal (6) ;
- mettre en oeuvre ladite séquence de décalage minimum de flux individuels, pour obtenir
ainsi une configuration de flux avec une occupation de bande équivalente à ladite
configuration de flux théorique.
2. Procédure selon la revendication 1, dans laquelle ladite phase d'échange entre les
séries de tranches (6) est mise en oeuvre avec les étapes suivantes consistant à :
a) créer un premier tableau dans lequel chaque rangée donne, pour chaque flux dont
la position dans la configuration de flux théorique diffère de la position de configuration
initiale, un indice de référence associé audit flux et une paire de valeurs indiquant
la série de tranches source et la série de tranches de destination respectivement
;
b) créer une liste de toutes les paires de valeurs présentes au moins une fois dans
le premier tableau, trier par ordre décroissant lesdites paires de valeurs en fonction
du nombre de fois où chaque paire apparaît dans ledit premier tableau ;
c) échanger les séries de tranches (6) correspondant aux valeurs indiquées par la
première paire dans ladite liste à partir du haut, et effacer de la liste ladite première
paire et toutes les autres paires dans lesquelles l'une ou l'autre des valeurs contenues
dans ladite première paire apparaît ;
d) répéter l'étape c) jusqu'à ce que toutes les paires dans ladite liste soient terminées.
3. Procédure selon la revendication 1 ou 2, dans laquelle ledit réseau de transport comprend
au moins une série de tranches de réserve normalement inoccupées par un flux, et dans
laquelle lesdites phases qui définissent une séquence de décalage minimum des flux
individuels, et qui mettent en oeuvre ladite séquence, sont mises en oeuvre avec les
étapes suivantes consistant à :
e) créer un second tableau (10), montrant l'interdépendance des flux ;
f) sélectionner un premier flux parmi ceux qui doivent être décalés ;
g) ajouter dans ledit second tableau (10), pour ledit flux sélectionné, un nombre
de rangées égal au nombre de flux qui occupent, même partiellement, la position finale
dudit flux sélectionné, écrire une paire d'indices de référence montrant le flux sélectionné
et le flux occupant la position finale dans chacune desdites rangées, ou au cas où
ladite position finale est libre, une paire d'indices de référence dans laquelle un
premier indice indique le flux sélectionné et un second indice montre de manière conventionnelle
que la position finale est libre (0) ;
h) répéter l'étape g) sélectionnant les flux qui occupent la position finale du flux
sélectionné précédemment, un à la fois et de manière récursive, jusqu'à ce qu'une
telle position finale soit libre ou soit occupée par un flux qui a déjà été sélectionné
précédemment ;
i) vérifier dans ledit second tableau la présence d'une dépendance circulaire entre
deux flux ou plus, si une telle occurrence est présente, commencer à décaler l'un
des flux dans ladite dépendance circulaire sur une série de tranches de réserve libres
et pour toutes les paires dans ledit second tableau ayant comme valeur indicative
de la position finale du flux l'indice indicateur dudit flux décalé, remplacer ledit
indice par une valeur (0) indiquant de manière conventionnelle que la position finale
est libre ;
j) rechercher dans ledit second tableau des paires ayant comme indice indicateur de
la position finale du flux ladite valeur conventionnelle (0) indiquant que la position
finale est libre, et traiter, pour chacune desdites paires en décalant le flux correspondant
sur la position finale correspondante et effacer la rangée correspondante à ladite
paire du même tableau ; pour toutes les paires dudit second tableau ayant comme valeur
indicative de la position finale du flux l'indice indicatif dudit flux décalé, remplacer
ledit indice par une valeur (0) indiquant de manière conventionnelle que la position
finale est libre ;
k) répéter les étapes i) et j) jusqu'à ce que le second tableau soit vide ;
l) sélectionner un nouveau flux parmi ceux qui doivent être décalés et répéter l'étape
g) et les étapes suivantes.
4. Procédure selon l'une des revendications 1 à 3, dans laquelle lesdites séries de tranches
(6) dans lesquelles lesdits flux sont initialement colocalisés sont des séries de
tranches d'un premier sous-réseau dudit réseau de transport.
5. Procédure selon la revendication 4, dans laquelle lesdites séries de tranches de réserve
sont des séries de tranches d'un second sous-réseau dudit réseau de transport.
6. Procédure selon la revendication 5, dans laquelle ledit premier sous-réseau et ledit
second sous-réseau sont des réseaux annulaires.
7. Procédure selon l'une quelconque des revendications précédentes, dans laquelle ledit
réseau de transport est un réseau du type SDH ou SONET et lesdites tranches sont des
intervalles de temps.
8. Procédure selon l'une quelconque des revendications 1 à 6, dans laquelle ledit réseau
de transport est un réseau du type WDM et lesdites tranches sont des tranches λ, c'est-à-dire
des longueurs d'onde.
9. Procédure selon l'une quelconque des revendications 1 à 6, dans laquelle ledit réseau
de transport est un réseau du type SDM et lesdites tranches sont des intervalles spatiaux.
10. Procédure selon l'une quelconque des revendications 1 à 6, dans laquelle ledit réseau
de transport est un réseau du type FDM et lesdites tranches sont des intervalles de
fréquence.
11. Dispositif pour la gestion centralisée d'un réseau de transport, dans lequel des données
sont agencées dans des flux de données de circuit colocalisés dans une pluralité de
séries de tranches (6), comprenant un système pour trier lesdits flux dans lesdites
séries de tranches, caractérisé en ce que ledit système utilise une procédure pour optimiser la bande selon l'une quelconque
des revendications précédentes.
12. Programme informatique comprenant des moyens à code de programme informatique adaptés
pour effectuer toutes les étapes de l'une quelconque des revendications 1 à 10 lorsque
ledit programme est exécuté sur un ordinateur.
13. Programme informatique selon la revendication 12 mise en oeuvre sur un support lisible
par ordinateur.